There are internet headers in every email message. You can set your email browser to display them. They will show from what IP address and domain the email was sent. If the domain does not contain that IP, you know it was spoofed. You can post this info(just the sending domain and IP) here for people to review.proofseeker said:
But the likelyhood of finding anything out in that way is pretty slim. The number of people with the knowledge to spoof email is quite low, so it's probably more likely that someone got ahold of your boyfriend's username and password and sent an email from his account. In which case, even if it really was sent from his account, that would have little implication for your relationship.
You've only got one post on this site, and it affords a lot of anonymity, so you might consider posting your full problem here in the random section of the forum. Just a thought. Use your discretion.